A judge will not unseal search warrants in the case of a man accused of pushing his wife to her death off a cliff in Colorado’s Rocky Mountain National Park.

U.S. District Judge R. Brooke Jackson on Monday denied prosecutors’ request to unseal about 20 search warrants authorities obtained over two years while investigating 58-year-old Harold Henthorn. A grand jury this month indicted Henthorn on a first-degree murder charge in the Sept. 29, 2012 death of his second wife, 50-year-old Toni Henthorn.

Prosecutors say Henthorn pushed her more than 140 feet off a ledge while on an anniversary hike in the park. Court records show investigators used photographic and electronic surveillance in building their case.

Henthorn is also being investigated for the death of his first wife 17 years earlier.